Power semiconductor device

1. A power semiconductor device, comprising: a portion, comprising: a ceramic board; a plurality of sides provided on the ceramic board, the plurality of sides and the ceramic board defining a space filled with a thermal insulator; and a silicon-carbide power semiconductor element enclosed within the thermal insulator; and an external package enclosing the portion, wherein a thermal conductivity of the external package is lower than a thermal conductivity of the plurality of sides.

2. The power semiconductor device according to claim 1 , wherein the thermal insulator has a thermal conductivity lower than the thermal conductivity of the external package.

3. The power semiconductor device according to claim 1 , wherein the external package comprises a thermal buffer element having a specific heat higher than a specific heat of the external package.

4. A power semiconductor device, comprising: an electrode; a first portion, comprising: a ceramic board; a plurality of walls in communication with the ceramic board forming a space filled with a plastic resin; and a silicon carbide power semiconductor element mounted to the electrode in the space filled with the plastic resin; and a second portion comprising a silicon power semiconductor element, the silicon power semiconductor element being mounted to the electrode outside said space and connected to the silicon carbide power semiconductor, wherein the first and second portions are packaged.

5. The power semiconductor device according to claim 4 , further comprising a thermal insulator provided between the first portion and the second portion.

6. The power semiconductor device according to claim 5 , wherein the thermal insulator is made of a plastic resin.

7. The power semiconductor device according to claim 4 , further comprising: a heat sink contacting the silicon power semiconductor element of the second portion to radiate heat there from, wherein the heat sink has a non-contact with the silicon carbide power semiconductor element of the first portion.

8. The power semiconductor device according to claim 4 , further comprising: a heat sink that radiates heat from said second portion, and a heat transmittance region having a thermal conductivity lower than 10 W/(m·K) provided between the first portion and the heat sink.

9. The power semiconductor device according to claim 4 , wherein the electrode has a partially widened region.

10. The power semiconductor device according to claim 4 , wherein the silicon carbide power semiconductor device is mounted onto the electrode by pressure connection.

11. The power semiconductor device according to claim 4 , wherein the silicon carbide power semiconductor element is a transistor or a diode.